NAME

GPIB::hpserial - Perl-GPIB interface to many HP instruments with serial ports

SYNOPSIS

use GPIB;

# /etc/pgpib.conf entry
# Flag has the following bits:
#   0x0001      Use RTS/CTS flow control sending to device
# name    driver              port        speed   TMO     EOS     FLAG
HP33120A  GPIB::hpserial      /dev/ttyS1  9600    T3s     0x0a    0x0001

# Perl program using /etc/pgpib.conf 
use gpib::hp33120a;
$g = gpib::hp33120a->new("HP33120A");
$g->freq(1000000.0);  # Set Frequency to 1MHz

# Perl program accessing serial driver with /etc/pgpib.conf
use gpib::hp33120a;
$g = gpib::hp33120a->new("gpib::hpserial", "/dev/ttyS1", 9600, gpib->T3s, 0x0a, 1);
$g->freq(2000000.0);  # Set Frequency to 2MHz

DESCRIPTION

gpib::hpserial is an interface module for accessing HP test equipment with RS-232 ports. This module is not normally called directly, but is called by the gpib module according an entry in /etc/pgpib.conf or by calling gpib->new and passing gpib::hpserial as the first parameter.

The module is an XS module that uses termios and so it is a Unix-only module. The module uses setitimer() so it's probably a bad idea to use alarm() in conjunction with calls to serial devices.

These devices are generally 9600 baud, 8-bit, no parity devices that require hardware flow control. Sadly, hardware flow control is always a bit awkward. The HP devices use DTR/DSR pins for flow control. Linux only supports RTS/CTS handshaking so you pretty much have to build your own serial cable that connects DTR on the instrument (pin-4 of DB-9) to CTS on the host (pin-5 of DB-9). One of those little RS-232 boxes with a bunch of activity LEDs and the HP instrument manual are indespensible even though it seems like serial connections should be really simple.

You can choose to not use hardware flow control with a bit in the settings in /etc/pgpib.conf, but I don't recommend it except for debugging. The HP instruments appear to have the world's slowest microcontrollers and their tiny buffers overflow often at 9600 baud, even on simple commands.

Here's a test to see if you've got flow control sorted out properly. On an HP33120A the following piece of code should cause very regular relay chatter as the output switches between sine wave and square wave. If the program hangs or starts beeping and flashing error lights on the instrument, the serial port flow control wires are probably not wired correctly:

use gpib::hp33120a;

$g = gpib::hp33120a->new("HP33120A");
while (1) {
   $g->shape(SQU);
   $g->shape(SIN);
}

The design goal is that you should be able to hook up a piece of HP test equipment with both a GPIB port and a serial port using either interface and software should work identically. The only difference being an entry in the /etc/pgpib.conf describing the interface to the device.

AUTHOR

Jeff Mock, jeff@mock.com

SEE ALSO

perl(1), gpib(3), gpib::ni(3), gpib::rmt(3), gpib::hp33120a(3).